Method of threading drawtwister



March 28, 1961 J. B. STEEN METHOD OF THREADING DRAWTWISTER Filed Oct. 30, 1958 I INVENTOR.

JOHN B. STEEN AT OR Y.

United rates Eistent G METHOD F THREADING DRAWTWESTER John B. Steen, Asheville, N.C., assiguor to American Enka Corporation, Enka, N.C., a corporation of Delaware Filed Oct. 30, 1958, Ser. No. 770,849

3 Claims. (Cl. 57-157) This invention relates in general to the drawtwisting of artificial yarn and more particularly to a method of passing yarn of irregular or generally rectangular shaped cross-section through a drawtwisting apparatus.

In a conventional drawtwisting operation yarn is delivered at a first rate of speed by feed rollers to a drawing zone in which one or more draw pins are situated. The yarn is withdrawn from this drawing zone by draw rollers rotating at a rate of speed greater than that of the feed rollers whereby stretch may be imparted. The pin or pins in the drawing zone tend to localize the draw point and produce uniformly drawn yarn.

The drawn yarn is usually fed from the draw rollers directly to a ring twister collecting means comprising, for example, a spindle rotating about a vertical axis, a ring rail reciprocable along the spindle axis, a ring traveler slidably supported on the ring rail and one or more guides mounted on the extended axis of and above the spindle. Rotation of the spindle and traveler relative to the linear speed of yarn travel can be controlled to produce a desired twist during yarn collection.

When conventional yarns, i.e., yarns having a generally circular configuration in cross-section, are processed on a drawtwisting apparatus of the type described, twist torque produced therein by the twister take-up tends to cause rolling of these yarns laterally over the surface of the draw roller. The direction in which the yarn tends to roll of course is determined by the type twist imparted. A Z-twist will create a tendency for yarn to roll in one direction, while S-twist will produce torque in the opposite direction.

There are at least three reasons why yarn of this type does not roll off the end of the draw rollers. In the first place, the rollers and guides are placed in alignment so as to facilitate tracking. Moreover, the tension in the drawn yarn tends to maintain a straight path between successive contact points. Accordingly, any tendency for the yarn to bend out of alignmentis opposed by the guides and tensioned yarn. Moreover, if the yarn is of generally circular cross-section, the friction developed between the drive surface and the filaments in contact therewith is very low. Consequently, only a small amount of the torque imparted to the yarn by the twister take-up is available as a driving force to cause deviation from the path defined by the draw roller and guide. As a result of this, instead of rolling laterally with respect to the draw roller, this yarn continuously slides over the surface thereof. It can be seen, therefore, that the yarn is biased in a direction laterally of the draw rollers, but roll-off does not occur because of the sliding action.

When low-filament or other special types of yarn are processed, however, the foregoing phenomena does not exist. Special yarns of the type herein under consideration may be twoand four-filament yarn used in the hosiery industry or other types having an elongated cross-sectional shape. The cross-sectional shape of yarn used herein is not to be confused with the cross-sectional shape of the individual filaments, which is generally circular. The

Patented Mar. 28, 1961 EQC terminology used may be explained best by reference to yarn formed from two cylindrical filaments. This twofilament yarn is generally rectangular in cross-section or has a length, which may be called the major axis, twice the width, which may be referred to as the minor axis.

When this low-filament yarn is passed over a smooth surface under tension the filaments tend to flatten out so that each one contacts the surface. It has been found that the frictional force developed between low-filament yarn and the draw roller, for example, is greater than that described in connection with conventional yarn of circular cross-section. Consequently, more of the torque produced by the twister take-up is applied at the contact point, and this type yarn has been found to roll off the draw roller almost immediately after threading up on a drawtwisting machine.

An obvious solution to this roll-off problem, of course, would be the addition of more guides around the draw roller in order to restrain lateral movement of the yarn. Additional guides are objectionable, in the first place, however, from an economical standpoint. Not only must more guides be purchased, it would be necessary to modify the drawtwisting apparatus to receive the same. Moreover, the use of more guides would entail at least one additional motion during threading up and this would necessarily lengthen the time required for this operation. Although small increments of time per spindle might seem insignificant, each operator is assigned one or more drawtwisting machines, and each machine contains a large number of spindles. volved could be considerable.

Another solution would be the substitution of a flanged roll for the draw roll. Theoretically, this is a sound proposal and should operate to restrain yarn movement. In practice, however, the cost of roller replacement is much too great to justify this expedient. Moreover, yarn very often is collected on the draw roller during threading-up and subsequently removed during normal operation. Such removal would be impossible'if the roller were flanged.

One of the objects of this invention is to provide a method for restraining roll-off when passing low-filament yarn through a drawtwisting machine.

Another object of the present invention is to provide a method for threading a drawtwisting machine for use in processing low-filament yarn.

Still another object of this invention is to provide an economical modification to a drawtwisting apparatus to adapt the same for use in processing low-filament yarn.

A further object of the present invention is to provide a new and improved system for threading a drawtwisting apparatus to condition the same for processing special yarns having generally rectangular shapes in cross-section.

In accordance with the present invention, a conventional drawtwisting apparatus is modified so that the draw pin thereof can be used as a twist stop and as a restraining member to prevent lateral movement of yarn passing thereover. The customary passage of yarn from the draw rollers to the take-up is altered to permit utilization of the added draw pin function to prevent roll-off of low-filament yarn from the draw roller due to torque developed during twisting.

By the use of this invention, the roll-off problem mentioned can be obviated with a minimum of attention from the operator, with no additional guides, at very little expense, and with no increase in the time required for threading-up.

Other objects and advantages will become apparent upon study of the following detailed disclosure taken in conjunction with the appended drawings, wherein Figure l is a perspective view, partly in section, of that portion only of a drawtwisting machine necessary to Consequently, the overall time in-.

complete understanding of this invention, with particular emphasis being given to the passage of yarn from the draw rollers to the twister take-up; and

Figure 2 is a perspective view of one component of the apparatus shown in Figure l, and illustrating an alternative construction.

With attention now directed to Figure l, yarn 141 as shown is passed downwardly from the feed rollers (not illustrated) of a conventional drawtwisting machine indicated generally by reference numeral 11. The particular machine chosen for this discussion is provided with first and second draw pins 12, 13, respectively, although it should be understood that this invention is equally applicable to a machine utilizing only one draw pin. The left ends of pins 12, 13 are supported in cantilever fashion from the machine frame, also not shown.

Yarn passes from the second draw pin 13 onto draw roller .14 and from there to idler roller 15. The yarn is wrapped about these rollers 14, a number of turns in order to prevent longitudinal slippage between the yarn and roller surfaces. Draw roller 14 may be driven in any manner at any preferred speed, and also is supported in cantilever fashion from the machine frame. Generally, this roller is driven with a surface speed about three times that of the feed rollers in order to stretch the yarn by a ratio of about 3:1. As mentioned earlier, the curved surface of draw pins 12, 13 tend to localize the draw point between the feed and draw rollers, and produce a drawn yarn having a uniform cross-section.

In conventional practice, yarn is fed from the last wrap on idler roller 15 directly to pigtail guide 16, which guide is axially aligned with the spool 17 on ring twister generally indicated at 18. From the guide 16 the yarn is fed through ring traveler 20 to the spool and collected thereon. Traveler 20 is slidably mounted on ring rail 21 and the ring rail is reciprocated vertically in known manner by means not shown. Moreover, the spindle which supports spool 17 has not been illustrated but of course also is in axial alignment with the pigtail guide 16.

The known drawtwisting machine described above has been modified by the provision of a flange 22 on the end of draw pin 12. The pins 12, 13 are easily removed, usually by loosening lock screws, and can be replaced in a matter of seconds. Instead of substituting a new draw pin 12, the same function could be served by other means, such as providing a circumferential groove in the existing pin. In either event, the modified draw pin 12 serves additional functions. Not only does this pin contribute to localizing the draw point, it now serves to prevent or restrain lateral movement of the yarn passing thereover, and at least partially as a twist stop.

Attention is directed to the lateral spacing between that yarn initially passing over the draw pins, and that fed from idler roller 15. Yarn fed from the feed rollers to draw roller 14 passes near the supported ends of the draw pins, as shown, since this portion is in alignment with the drive surfaces of the rollers. Yarn fed from idler roller 15 back over the draw pin 12, however, is biased against the flange because of the torque produced by ring twister 18, as described earlier. In the thread-up shown, it will be assumed that S-twist biases the yarn toward the unsupported end of the draw roller 14 and draw pin 12, hence the term roll-oft.

It has been found that replacement or modification of draw pin 12 is the most economical way to obviate the roll-off problem. In order to utilize the flange 22 on this pin, it is necessary only to alter the normal yarn path indicated by dotted line 19. Instead of the known procedure, the yarn discharging from idler 15 is fed back over the draw pin 12 and then through pigtail guide 16 to the traveler 20. It will be seen that the yarn cannot roll oil the end of the draw pin because of the flange. Moreover, the presence of this restraining member also prevents roll-oil farther down the yarn at rollers 14, 15. .This occurs, probably, because the pin 12 functions not only as a means for restraining lateral yarn movement, but also as a twist stop. In other words, the pin eliminates, at least partially, the cause of roll-cit by preventing twist and the torque concomitant therewith from occurring in the yarn passing over these rollers.

In the event that Z-twist is produced in the yarn 10, it will be apparent that the opposite torque developed thereby will bias the yarn toward the supported end of the draw rollers on a conventional machine and toward the supported ends of the draw pins on a machine modified in accordance with this invention. Although roll-oil of course could not occur, lateral shifting of the yarn would result in filament damage because of the resulting contact between adjacent wraps. This yarn damage could be eliminated to some extent by reverse threading. In other Words, the yarn could be wrapped about rollers 14, 15 from the unsupported end toward the supported end. Such, however, is not geometrically feasible.

Consequently, if the drawtwisting machine is to be used producing boti S and Z twist in drawn yarn, the modification shown in Figure 2 should be used. The unsupported end of alternative draw pin 12a terminates in a flange 22a similar to that described in the first embodiment. As stated earlier, it will be assumed that flange 22a prevents yarn roll-off due to torque produced by S-twist. An additional flange 23 is fixed in spaced relationship to the flange 22a on pin 12a. Should it be desired to collect yarn it with a Z-twist, this latter flange will prevent gradual shifting of the drawn yarn along pin 12:; into contact with that wrap near the supported end. Although only one of the flanges 22a, 23 will be used in any given operation, the provision of two flanges permits use of the drawtwisting machine for producing either 3- or Z-twist in the special type yarn under consideration. The yarn of course is threaded between these two flange in the manner shown.

The use of a flanged draw pin fully obviates the rolloff problem encountered when processing yarn having an elongated or generally rectangular shape in cross-section. While other solutions obviously are possible, this has been found to be the most economical and the least time consuming. Either of the draw pins 12, 13 could of course be used. Since pin 12 is nearer both to the guide 16 and to the idler roller 15, this pin is the obvious choice. The same principles of this invention apply even if only one draw pin is used. Either a groove or a flange should be provided near the end of the pin, or at least in alignment with the last wrap coming off idler 15. It has been found that an L-shaped draw pin does not operate as satisfactorily as the flanged type described since the yarn is wrapped substantially around the pin and thereby requires roll-ofl preventing means for the full 360 periphery.

Inasmuch as other modifications utilizing the principles described will become apparent upon study of this disclosure, it is intended that the scopeof the present invention be limited only to the extent set forth in the following claims.

What is claimed is:

1. In a drawtwisting process for treating artificial yarn having an elongated cross-sectional shape including the steps of delivering said yarn at a first rate of speed to a drawing zone, withdrawing said yarn from said drawing zone at a second rate of speed considerably greater than the said first rate, localizing the draw point of yarn drawn in said drawing zone by passing the same in contact with at least one curved surface, and collecting drawn yarn while imparting twist and twist torque thereto, the improvement comprising the steps of passing the drawn yarn after withdrawal from said drawing zone back into contact with said curved surface, and restricting any lateral movement of said yarn relative to said surface which is induced by the aforesaid twist torque imparted during collection.

2. A drawtwisting process as set forth in claim 1 wherein the elongated cross-sectional shape of said artificial yarn is formed by about four filaments having uniform individual cross-sections.

3. A drawtwisting process as set forth in claim 1 wherein the elongated cross-sectional shape of said artificial yarn is formed by two filaments having uniform individual cross-sections.

References Cited in the file of this patent UNITED STATES PATENTS Heim Apr. 26, 1949 Pollock July 5, 1949 Lichtenberg Dec. 20, 1949 Nield Dec. 16, 1952 Lenk Aug. 7, 1956 Eshuis Oct. 14, 1958 

